1. Field of the invention
The present invention relates to an apparatus of the type used for helically assembling filaments or elongated flexible elements together to form a cable or the like.
2. Description of the Prior Art
U.S. Pat. No. 4,709,542 issued to Krafft on Dec. 1, 1987, discloses a stranding apparatus adapted to form stranded cables of infinite lengths.
More specifically, Krafft discloses a cable assembly apparatus having a rotating shaft which is provided with two integral supply reels which are respectively adapted to receive thereon a group of wire elements. The flyer assembly rotates around the supply reels for unwinding the groups of wire elements therefrom. The flyer assembly is rotated in the same direction as the two integral supply reels but at a speed which causes the wire elements to be unwound from the supply reels. A drive motor is directly connected to the rotating shaft for driving the integral supply reels. The flyer assembly is connected to the same drive motor but through a variable diameter pulley assembly so that the rotational speed of the flyer assembly is adjustable with respect to that of the integral supply reels. The apparatus further comprises a gathering assembly which is mounted for rotation with the flyer assembly for gathering and twisting the individual wire elements together or over a core element to form a cable. A take-up reel is disposed downstream from the gathering assembly to receive thereon the finished cable coming out from the center of the rotating shaft. A motor is coupled to the take-up reel to enable the same to be operated to draw the cable from the gathering assembly. The motor of the take-up reel may be adjusted to maintain a desired amount of tension in the cable to enhance the quality of the finished cable. However, it is the rates of rotation of the integral supply reels and of the flyer assembly which control the rate of production of the cable and thus the tension which is applied to the cable does not change the rate at which the cable is produced. Indeed, an increase of the rotational speed of the take-up reel does not change the rotational speed of the integral supply reels as the same are not allowed to freely rotate on the rotating shaft thereof. Accordingly, in order to obtain a desired length of twist per unit length of cable, the rotational speed of the flyer assembly must be adjusted relative to the rotational speed of the integral supply reels.
It is believed that the apparatus of the above described patent never gained commercial acceptance as the helical pitch of the final product and the amount of tension in each supply wire were overly difficult to control.
FIG. 8 illustrates a conventional apparatus 410 used in steel industries to helically assemble a plurality of individual strands together about a central core to form a steel cable.
The apparatus 410 generally comprises a rotatable tube 412 mounted to a frame structure 414 for rotation about a central axis, and a plurality of supply spools 416, 418, 420 and 422 mounted for rotation about respective transversal axes. The supply spools 416, 418, 420 and 422 have respective strands 424, 426, 428 and 430 wound thereon. A capstan 432 is disposed downstream of the tube 412 for pulling the strands 424, 426, 428 and 430 out of a matrice 434 provided at the downstream end of the tube 412 for helically assembling the individual strands 424, 426 and 428 together about the central strand 430. The spools 418, 420 and 422, which are disposed within the tube 412, are supported by respective non-rotatable cradles 436, whereas the spool 416, which is disposed upstream of the tube 412, may be supported by any suitable support structure (not shown). The tube 412 defines at an upstream end thereof a first central passage 438 for allowing the strand 424 of the supply spool 416 to access the interior of the tube 412. Furthermore, the tube 412 defines at a downstream end thereof a second central passage 440 for allowing the strand 430 of the spool 422 to pass through the apparatus 410 along the central axis without being twisted to form the central core of the cable. Pulleys 442 connected to the tube 412 are provided between the spools 416418, 420 and 422 along the central axis for engaging the strands 424, 426 and 428 before the same be directed to other pulleys 444 mounted to the external surface of the tube 412.
In operation, the capstan 432 is activated to advance strands 424, 426, 428 and 430 through the apparatus 410, while the tube 412 is driven in rotation to cause the strands 424, 426 and 428 to rotate about the central strand 430. It is noted that the strands 424, 426 and 428 are twisted onto themselves as they engage respective pulleys 442 and are untwisted when they leave the tube 412, i.e. when they pass over the last pulleys 444 disposed at the downstream end of the tube 412, thereby ensuring that each individual strand be untwisted in the assembled product. Finally, the strands 424, 426 and 428 are helically assembled together on the central strand 430 as they return to the central axis within the matrice 434. As seen in FIG. 8, the assembled product may be wound on a take-up spool 446 disposed downstream of the capstan 432.
Basically, the above stranding apparatus 410 is intended for producing steel cables formed of a plurality of strands helically assembled on a central core and is thus not well adapted for manufacturing twisted pair cables, such as those used for transmitting messages.
FIG. 9 illustrates a conventional apparatus 510 for manufacturing twisted pair cables, i.e. cables composed of two strands helically assembled together about a central axis. Such an apparatus generally comprises a main flyer 512 adapted to impart a double twist to a pair of strands 514 and 516 emanating from a matrice 518. The two strands 514 and 516 are wound on respective supply spools 520, 522 and directed onto two distinct rotating flyers 524 and 526 which are driven in rotation so as to suppress the twist which is imparted to the strands 514 and 516 in order to ensure that each strand 514, 516 be not twisted onto itself in the assembled product. The assembled product may be received on a take-up spool 528 disposed inside of an envelope defined by the rotational movement of the main flyer 512.
Although the above apparatus 510 performs satisfactorily in many applications, it has been found that there is a need for a simpler and less expensive apparatus which does not necessitate the utilisation of three flyers.